The provisions of Section 1204 of IBC are adopted by reference with the following modifications:
1. Revise Section 1204.1 to read:
"1204.1 General.
Every space intended for human occupancy shall be provided with natural light in accordance with Section 1204.2 or shall be provided with artificial light in accordance with Section 1204.3.
Exceptions:
1. In dwelling units and sleeping units in Group R, I-1, and I-2 occupancies, all living, dining, and sleeping rooms with a floor area of 70 square feet (6.5 m
2
) or more shall be provided with natural light in accordance with Section 1204.2 and artificial light in accordance with Section 1204.3.
2. In Group I-4 occupancies all living and sleeping rooms for persons receiving custodial care shall be provided with natural light in accordance with Section 1204.2 and artificial light in accordance with Section 1204.3.
3. In Group E occupancies, all regular classrooms shall be provided with natural light in accordance with Section 1204.2 and artificial light in accordance with Section 1204.3."
2. Revise Section 1204.2 and its subsections to read:
"1204.2 Natural light.
Where required, natural light shall be provided in accordance with Section 1204.2.1, 1204.2.2, 1204.2.3 or 1204.2.4. Openings shall comply with Sections 1204.2.5 and 1204.2.6.
1204.2.1 Direct natural light.
The room shall be provided with exterior openings with a net glazed area of at least 8 percent of the floor area of the room.
1204.2.2 Adjoining spaces.
For the purpose of natural lighting, any room is permitted to be considered as a portion of an adjoining room where at least one-half of the area of the common wall is open and unobstructed and provides an opening of not less than 10 percent of the floor area of the interior room or 25 square feet (2.32
m2), whichever is greater. The net glazed area of exterior openings shall be at least 8 percent of the aggregate floor area.
1204.2.3 Remote rooms.
A room without sufficient exterior openings is permitted to borrow natural lighting from an adjoining room that meets the requirements of Section 1204.2.1 if the remote room, adjoining room and exterior openings meet all of the following criteria:
1. The ceiling height in both the remote room and adjoining room shall be no less than 9 feet 4 inches (2844 mm) at the lowest point.
2. The top of the exterior glazing shall be no less than 9 feet (2743 m) above the finished floor.
3. The opening between the remote room and the adjoining room shall be parallel to the plane of the exterior glazed openings, as near as possible to the ceiling and either:
3.1. If open and unobstructed, shall have an area at least 8 percent of the floor area of the remote room or 25 square feet (2.32
m2), whichever is greater.
3.2. If equipped with transparent or translucent glazing, shall have a net glazed area at least 10 percent of the floor area of the remote room or 30 square feet (2.8
m2), whichever is greater.
4. The remote room shall be immediately adjacent to the adjoining room.
5. The net glazed area of exterior openings shall be at least 8 percent of the aggregate floor area of the adjoining room and remote room.
1204.2.4 Residential basements.
Where at least 40 percent of the net floor area of a Group R dwelling unit, not used as congregate living facilities, is located entirely above grade and provided with natural light in accordance with Section 1204.2.1 or 1204.2.2, basement spaces may be provided with natural light as follows:
1. Bedrooms shall have exterior openings with a net glazed area of at least 6 percent of the floor area of the room.
2. For habitable spaces other than bedrooms, the basement level, as a whole, shall be provided with exterior openings with a net glazed area of at least 4 percent of the aggregate floor area of all habitable spaces in the basement.
1204.2.5 Exterior openings.
Exterior openings required by Section 1204.2 for natural light shall open directly onto a public way or a yard or court complying with Section 1205.
Exceptions:
1. Required exterior openings are permitted to open into an open porch or exterior balcony where the open porch or exterior balcony meets all of the following criteria:
1.1. Abuts a public way, or a yard or court complying with Section 1205.
1.2. Has a ceiling height of not less than 7 feet (2134 mm).
1.3. Has a longer side, parallel to the plane of the openings, at least 55 percent open and unobstructed from finished floor to underside of surface above.
2. Skylights that are unobstructed to the sky are not required to open directly onto a public way, yard or court.
1204.2.6 Openings below grade.
Where openings below grade are used to provide required natural light, the outside horizontal clear space measured perpendicular to the opening shall be one and one-half times the depth of the opening. The depth of the opening shall be measured from the average adjoining ground level to the bottom of the opening."
3. Revise Section 1204.3 to read:
"1204.3 Artificial light.
Artificial light shall be provided that is adequate to provide an average illumination of 10 footcandles (107 lux) over the area of the room at a height of 30 inches (762 mm) above the floor level. Lighting outlets shall be provided as required in Section 210.70 of the Chicago Electrical Code.
Exception: Within dwelling units, wall switch-controlled receptacles shall be permitted in lieu of lighting outlets in accordance with Section 210.70(A)(1), exception 1 of the Chicago Electrical Code."
4. Revise Section 1204.4 by replacing "dwelling unit" with "single dwelling unit."
(Amend Coun. J. 6-25-21, p. 32180, Art. II, § 21; Amend Coun. J. 1-26-22, p. 43756, Art. II, § 15)